Frequently Asked Questions
Q: How deep will a metal detector/locator go?
A: This is the question most frequently asked. Unfortunately, it has no absolute answers. The following variables, in addition
to your own detector's capabilities, all have an effect on the answer.
1. Conductive properties of the soil: Heavily mineralized soil will tend to reduce the penetration power of your detector. Soil
mineralization may vary greatly, and you may have to re-ground balance your detector to adjust for soil mineralization;
unless, of course, your detector has automatic ground balancing. In this case, you may need to decrease sensitivity and/or
increase discrimination on models like the Fisher F series detectors, which has extraordinary sensitivity.
2. The length of time an object is buried: Various chemicals in the soil have a corrosive action on metal. Some metals corrode
faster than others. A modern zinc penny is attacked by these soil chemicals quite easily, whereas the action on copper and
silver is much less, and corrosive action on gold is hardly noticeable, if at all. As these chemicals eat away at the metal,
oxidation (rust) takes place, which is absorbed into the surrounding soil. This causes the soil to become more conductive,
which in turn makes the metallic object appear larger than it actually is and easier to detect. This is known as the "halo effect."
3. The size of an object: The larger the metallic object, the easier and deeper it can be detected. For example, a bucket can be
detected much easier than a single coin. The more surface area seen from above, the deeper the metallic object will be
4. The shape of an object: Every metallic object reradiates at least part of the signal transmitted by your metal detector. In this
way, objects function like additional antennas, and consequently their shape becomes important. Ring or loop-shaped
objects lying flat, on or under the ground, produce the best results; flat or dish-shaped objects are similarly easy to detect.
Rod-shaped items, especially when scanned end-on, are very difficult to detect unless they're made of iron and you're using a
ferromagnetic detector, such as the Fisher FX-3.
5. The degree of magnetization: With ferromagnetic locators, such as the FX-3, the degree of magnetization has a strong
influence on depth. A magnet, for example, can be detected at much greater depth than an equivalent mass of iron. The more
magnetization an object has, the deeper it can be sensed by a ferromagnetic metal detector.
Q: Regarding the size of search coils, is bigger better?
A: Several coil sizes are usually offered for each detector. Each size offers specific strengths and weaknesses. A small coil is
better than a larger coil for picking out good targets among many trash targets. The standard coils are all-purpose coils. It is
the most popular coil size, and it performs well under most conditions. Larger coils are best suited for low-trash areas. They
cover more ground and increase depth penetration 5-15 percent. However, larger coils are heavier, and some detector users
feel more comfortable during long searches if they use a smaller coil. Having more than one coil size is often helpful for
varying conditions you will encounter. Elliptical coils, which get into nooks and crannies easier, are also available. All Gold
Bug-2 coils are elliptical in shape and measure 6 1/2, 10 and 14 inches in length. A 10-inch elliptical coil is also available for the
some F series Fisher detectors and some Teknetics models as well. Its lighter weight makes it the favorite of Treasure
Hunters who attend competition hunts.
Q: How does discrimination work?
A: A better word for discriminator is perhaps "differentiator." At minimum or no discrimination, all metal within the detectable
range is detected. As you slowly increase discrimination, small pieces of metallic trash and ground mineralization are ignored
(rejected). As you increase the discrimination, pull tabs, small nails, foil, and even some good targets (such as gold rings and
nickels) will be rejected. The best way to learn the discrimination points (the lowest discrimination setting at which an object is
rejected) of your detector is to scatter some sample targets, such as coins, pull tabs, and foil on the ground from 1-2 feet
apart. Starting at 0, or your detector's lowest discrimination point, scan each target. Gradually increase discrimination and
record the results. With practice, you should be able to determine whether or not to dig by listening closely to the target
The Fisher Gemini-3 and TW-6 "two-box" metal detectors can locate large metallic objects at great depthsobjects like pipes,
cables and treasure caches. These "two-box" detectors consist of a signal-receiver box and a signal-transmitter box
connected by a handle.
Q: What is the sensitivity control and how is it used?
A: The sensitivity control on metal detectors is probably the most misunderstood control on the instrument. Sensitivity is
usually set to its maximum level and ignored. This does not always allow for maximum operation of the detector. To use an
analogy, think of the sensitivity control as the throttle of a car. You don't drive everywhere at full speed. In fact, posted speed
limits are for normal conditions. But what about rain, snow, or even high wind? Of course, you decrease your speed.
Likewise, you should adjust your sensitivity control for varying conditions. Heavy ground mineralization, nearby power
transformers, and nearby radio stations are all reasons to lower your sensitivity. Although you might experience a slight loss
of depth, you may be losing more good targets than you think by listening to the false signals and chatter of high sensitivity.
Q: Why do serious metal detectorists use headphones?
A: Headphones can greatly reduce outside noise (wind, waves, traffic, etc.). They also enhance the audio target signal, which
will help you determine which targets to dig and which targets to ignore. Overall, a good set of headphones will improve the
number of your good finds and greatly reduce the time you spend digging trash. Headphones also reduce distractions,
extend battery life and keep you from attracting unwanted attention from curious onlookers. Headphones make faint, deep
target signals easier to hear. No additional batteries are required for headphones.
Q: What are false signals?
A: False signals are sometimes called "phantom" signals. They occur any time your detector responds to metal when there is
actually no metal there. False signals are most often caused by naturally occurring iron oxides, such as magnetite and
hematite. Magnetite is the primary constituent of the "black sand" that commonly occurs in placer gold deposits. If your
detector has a manual ground-balance or ground grab adjustment, you can usually tune out false signals. Sometimes you
may need to ground tune frequently if the mineralization of the soil changes abruptly as you move from one place to another.
If ground mineralization is excessive, turning down your detector's sensitivity may be the only solution.
Q: Which detector is best for finding large, deep targets?
A: A "two-box" detector, such as the Fisher Gemini-3 or TW-6, is best for finding large, deep targets, such as caches (hidden
treasure troves) or buried pipes and cables. But using a "two-box" detector on a connecting handle is different from using a
standard, hand-held metal detector. Although it goes deeper, the smallest metallic object you can hope to find with a
"two-box" detector is about the size of a cantaloupe melon, even if the melon-sized object is resting on top of the ground.
However, that same melon-sized object may be detected at a depth of up to 6 feet with a Fisher Gemini-3 or TW-6. Maximum
depth with these "two-box" detectors is achieved by carrying the unit low to the ground, suspended by a strap. An extra-long
handle is available for the Gemini-3 and TW-6 that also increases depth penetration by widening the separation of the boxes
on the handle.